Angle- and size-dependent characteristics of incoherent Raman and fluorescent scattering by microspheres. 2. Numerical simulation

The results of numerical simulation of inelastic scattering by microspheres with the use of a dipole model are presented. The formulas that are derived speed up the computation, thereby permitting larger-sized microspheres to be studied. The angular scattering cross section and depolarization are calculated for a wide range of size parameters as well as for different orientations of incident wave polarization. Calculations performed with small incremental changes in size permit the influence of morphology-dependent resonance (MDR) on the power and angular distribution of scattered radiation to be studied. TM and TE types of MDR produce enhanced scattering of the incident wave with vertical and horizontal polarization; the corresponding shape of the phase function becomes oscillatory. Special attention is paid to the simulation of backward scattering by water droplets, which is important for Raman lidar applications.     

Simulation of high-resolution x-ray zone plates

A full-wave approach to quantitative characterization of x-ray zone plate lenses is proposed. Distributed focusing efficiency eta(z) of a multifocus optical element is defined as the energy flux through the Airy disk of a reference perfect lens with variable focal length z. Maxima of this function characterize diffraction efficiencies and spatial resolution of the zone plate foci. The parabolic wave equation is used to take into account diffraction effects inside the optical element. Rough and fuzzy interface models are introduced to describe realistic zone profiles. Numerical simulation reveals the limited capability of zone width reduction to improve the zone plate imaging performance. The possibilities of second-order focus enhancement by optimization of the zone plate thickness, line-to-space ratio, and zone tilt are studied numerically.     

Career Anchors and Cross-Cultural Adjustment Among Expatriates in a Non-Profit Organization

Based on a sample of 189 expatriate managers working for a non-profit organization (NPO), we pursue two objectives in this paper. First, we address the lack of knowledge on expatriates working in the non-profit sector by exploring their dominant career anchors. Our analysis reveals that the dominant anchors are internationalism, dedication to a cause, and lifestyle. Second, we draw on person-environment fit theory to theorize and test the previously unexplored linkages between expatriates’ career anchors and cross-cultural adjustment (CCA). Our analysis shows that different career anchors are positively associated with different dimensions of CCA: autonomy, security, dedication to a cause, and pure challenge with general living adjustment; dedication to a cause, pure challenge, and internationalism with interactional adjustment; and functional competence, managerial competence, pure challenge, and internationalism with work adjustment. Overall, the study is one of the first attempts to explore career anchors and their linkages to CCA among expatriates in NPOs.     

Sensitivity analysis of LP-MPC cascade control systems

Model predictive control (MPC) has found wide application in the chemical process industry as well as other industrial sectors. Commercial MPC systems are typically implemented in conjunction with a steady-state linear or quadratic programming optimizer, whose key functions are to track the economic optimum and to provide feasible set-points to the model predictive controller. The two-level system is complementary to real-time optimization which typically utilizes more complex models and is executed less frequently. Despite the widespread adoption of LP-MPC systems, occurrences of poor performance have been reported, where large variations in the computed set-points were observed. In this paper, we analyze the sensitivity of the LP solution to variation in the LP model bias, through which feedback to the LP layer occurs. We consider both multi-input, single-output (MISO) and multi-input, multi-output (MIMO) systems. Principles are illustrated through graphical representation as well as case studies. The performance of the two-level LP-MPC closed-loop system is evaluated and explained using results of the LP sensitivity analysis.     

Merging enriched Finite Element triangle meshes for fast prototyping of alternate solutions in the context of industrial maintenance

A new approach to the merging of Finite Element (FE) triangle meshes is proposed. Not only it takes into account the geometric aspects, but it also considers the way the semantic information possibly associated to the groups of entities (nodes, faces) can be maintained. Such high level modification capabilities are of major importance in all the engineering activities requiring fast modifications of meshes without going back to the CAD model. This is especially true in the context of industrial maintenance where the engineers often have to solve critical problems in very short time. Indeed, in this case, the product is already designed, the CAD models are not necessarily available and the FE models might be tuned. Thus, the product behaviour has to be studied and improved during its exploitation while prototyping directly several alternate solutions. Such a framework also finds interest in the preliminary design phases where alternative solutions have to be simulated. The algorithm first removes the intersecting faces in an n-ring neighbourhood so that the filling of the created holes produces triangles whose sizes smoothly evolve according to the possibly heterogeneous sizes of the surrounding triangles. The hole-filling algorithm is driven by an aspect ratio factor which ensures that the produced triangulation fits well the FE requirements. It is also constrained by the boundaries of the groups of entities gathering together the simulation semantic. The filled areas are then deformed to blend smoothly with the surroundings meshes.     

Neural integrator: a sandpile model

We investigated a model for the neural integrator based on hysteretic units connected by positive feedback. Hysteresis is assumed to emerge from the intrinsic properties of the cells. We consider the recurrent networks containing either bistable or multistable neurons. We apply our analysis to the oculomotor velocity-to-position neural integrator that calculates eye positions using the inputs that carry information about eye angular velocity. By analyzing this system in the parameter space, we show the following. The direction of hysteresis in the neuronal response may be reversed for the system with recurrent connections compared to the case of unconnected neurons. Thus, for the NMDA receptor-based bistability, the firing rates after ON saccades may be higher than after OFF saccades for the same eye position. The reversal of hysteresis occurs in this model only when the size of hysteresis differs from neuron to neuron. We also relate the macroscopic leak time constant of the integrator to the rate of microscopic spontaneous noise-driven transitions in the hysteretic units. Finally, we investigate the conditions under which the hysteretic integrator may have no threshold for integration.     

Remote plasma-enhanced CVD of silicon nitride films: effects of diluting nitrogen with argon. Part II: effect of nitrogen plasma parameters on layer characteristics

In Part I we reported the results of an emission spectroscopic study of the plasma obtained in an SiH₄–N₂–Ar mixture. It was shown that argon in metastable electronic excited states provides a high concentration of atomic nitrogen. In this part we report the results of a study of the influence of argon dilution on the growth rate, composition and properties of silicon nitride films. The exact influence of nitrogen dilution with argon depends on the process parameters and on the method of coupling of the RF power, but it is found in general that a high concentration of atomic nitrogen leads to changes in the relative amounts of Si–H_j and N–H_i bonds and in the Si/N ratio of deposited films. In particular, it is shown that hydrogen incorporation can be reduced and improved stoichiometry can be obtained. © 1998 John Wiley & Sons, Ltd.     

Surface Domain Structures and Mesoscopic Phase Transition in Relaxor Ferroelectrics

Relaxor ferroelectrics are a prototypical example of ferroic systems in which interplay between atomic disorder and order parameters gives rise to emergence of unusual properties, including non‐exponential relaxations, memory effects, polarization rotations, and broad spectrum of bias‐ and temperature‐induced phase transitions. Despite more than 40 years of extensive research following the original discovery of ferroelectric relaxors by the Smolensky group, the most basic aspect of these materials – the existence and nature of order parameter – has not been understood thoroughly. Using extensive imaging and spectroscopic studies by variable‐temperature and time resolved piezoresponse force microscopy, we find that the observed mesoscopic behavior is consistent with the presence of two effective order parameters describing dynamic and static parts of polarization, respectively. The static component gives rise to rich spatially ordered systems on the ～100 nm length scales, and are only weakly responsive to electric field. The surface of relaxors undergoes a mesoscopic symmetry breaking leading to the freezing of polarization fluctuations and shift of corresponding transition temperature.     

Comparison of Non-Equilibrium Green’s Function and Quantum-Corrected Monte Carlo Approaches in Nano MOS Simulation

In this paper, we present a comparative study between non-equilibrium Green’s function and quantum-corrected Monte Carlo approaches for an ultra-short channel MOSFET. As a result, we have found that the both models are equivalent in the simulation of quantum transport in a nano-scale MOSFET. We will also demonstrate that impurity scattering in the source region and plasmon scattering at the drain-end of the channel especially influence the drain current based on the quantum-corrected Monte Carlo approach.     

A framework for formal modeling and analysis of organizations

A new, formal, role-based, framework for modeling and analyzing both real world and artificial organizations is introduced. It exploits static and dynamic properties of the organizational model and includes the (frequently ignored) environment. The transition is described from a generic framework of an organization to its deployed model and to the actual agent allocation. For verification and validation of the proposed model, a set of dedicated techniques is introduced. Moreover, where most computational models can handle only two or three layered organizational structures, our framework can handle any arbitrary number of organizational layers. Henceforth, real-world organizations can be modeled and analyzed, as illustrated by a case study, within the DEAL project line